profile: Convert to hotplug state machine

Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs. A lot of code is removed because
the for-loop is used and create_hash_tables() is removed since its purpose
is covered by the startup / teardown hooks.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153337.649867675@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 66 insertions, 116 deletions

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 15d46d2a1d16..ace5ad0fc3ec 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -16,6 +16,7 @@ enum cpuhp_state {
         CPUHP_X86_APB_DEAD,
         CPUHP_WORKQUEUE_PREP,
         CPUHP_HRTIMERS_PREPARE,
+        CPUHP_PROFILE_PREPARE,
         CPUHP_TIMERS_DEAD,
         CPUHP_NOTIFY_PREPARE,
         CPUHP_BRINGUP_CPU,
diff --git a/kernel/profile.c b/kernel/profile.c
index c2199e9901c9..2dbccf2d806c 100644
--- a/kernel/profile.c
+++ b/kernel/profile.c
@@ -328,68 +328,57 @@ out:
         put_cpu();
 }
 
-static int profile_cpu_callback(struct notifier_block *info,
-                                        unsigned long action, void *__cpu)
+static int profile_dead_cpu(unsigned int cpu)
 {
-        int node, cpu = (unsigned long)__cpu;
         struct page *page;
+        int i;
 
-        switch (action) {
-        case CPU_UP_PREPARE:
-        case CPU_UP_PREPARE_FROZEN:
-                node = cpu_to_mem(cpu);
-                per_cpu(cpu_profile_flip, cpu) = 0;
-                if (!per_cpu(cpu_profile_hits, cpu)[1]) {
-                        page = __alloc_pages_node(node,
-                                        GFP_KERNEL | __GFP_ZERO,
-                                        0);
-                        if (!page)
-                                return notifier_from_errno(-ENOMEM);
-                        per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
-                }
-                if (!per_cpu(cpu_profile_hits, cpu)[0]) {
-                        page = __alloc_pages_node(node,
-                                        GFP_KERNEL | __GFP_ZERO,
-                                        0);
-                        if (!page)
-                                goto out_free;
-                        per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
-                }
-                break;
-out_free:
-                page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
-                per_cpu(cpu_profile_hits, cpu)[1] = NULL;
-                __free_page(page);
-                return notifier_from_errno(-ENOMEM);
-        case CPU_ONLINE:
-        case CPU_ONLINE_FROZEN:
-                if (prof_cpu_mask != NULL)
-                        cpumask_set_cpu(cpu, prof_cpu_mask);
-                break;
-        case CPU_UP_CANCELED:
-        case CPU_UP_CANCELED_FROZEN:
-        case CPU_DEAD:
-        case CPU_DEAD_FROZEN:
-                if (prof_cpu_mask != NULL)
-                        cpumask_clear_cpu(cpu, prof_cpu_mask);
-                if (per_cpu(cpu_profile_hits, cpu)[0]) {
-                        page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
-                        per_cpu(cpu_profile_hits, cpu)[0] = NULL;
+        if (prof_cpu_mask != NULL)
+                cpumask_clear_cpu(cpu, prof_cpu_mask);
+
+        for (i = 0; i < 2; i++) {
+                if (per_cpu(cpu_profile_hits, cpu)[i]) {
+                        page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[i]);
+                        per_cpu(cpu_profile_hits, cpu)[i] = NULL;
                         __free_page(page);
                 }
-                if (per_cpu(cpu_profile_hits, cpu)[1]) {
-                        page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
-                        per_cpu(cpu_profile_hits, cpu)[1] = NULL;
-                        __free_page(page);
+        }
+        return 0;
+}
+
+static int profile_prepare_cpu(unsigned int cpu)
+{
+        int i, node = cpu_to_mem(cpu);
+        struct page *page;
+
+        per_cpu(cpu_profile_flip, cpu) = 0;
+
+        for (i = 0; i < 2; i++) {
+                if (per_cpu(cpu_profile_hits, cpu)[i])
+                        continue;
+
+                page = __alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
+                if (!page) {
+                        profile_dead_cpu(cpu);
+                        return -ENOMEM;
                 }
-                break;
+                per_cpu(cpu_profile_hits, cpu)[i] = page_address(page);
+
         }
-        return NOTIFY_OK;
+        return 0;
+}
+
+static int profile_online_cpu(unsigned int cpu)
+{
+        if (prof_cpu_mask != NULL)
+                cpumask_set_cpu(cpu, prof_cpu_mask);
+
+        return 0;
 }
+
 #else /* !CONFIG_SMP */
 #define profile_flip_buffers()          do { } while (0)
 #define profile_discard_flip_buffers()  do { } while (0)
-#define profile_cpu_callback            NULL
 
 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 {
@@ -531,83 +520,43 @@ static const struct file_operations proc_profile_operations = {
         .llseek         = default_llseek,
 };
 
-#ifdef CONFIG_SMP
-static void profile_nop(void *unused)
-{
-}
-
-static int create_hash_tables(void)
+int __ref create_proc_profile(void)
 {
-        int cpu;
-
-        for_each_online_cpu(cpu) {
-                int node = cpu_to_mem(cpu);
-                struct page *page;
-
-                page = __alloc_pages_node(node,
-                                GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
-                                0);
-                if (!page)
-                        goto out_cleanup;
-                per_cpu(cpu_profile_hits, cpu)[1]
-                                = (struct profile_hit *)page_address(page);
-                page = __alloc_pages_node(node,
-                                GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
-                                0);
-                if (!page)
-                        goto out_cleanup;
-                per_cpu(cpu_profile_hits, cpu)[0]
-                                = (struct profile_hit *)page_address(page);
-        }
-        return 0;
-out_cleanup:
-        prof_on = 0;
-        smp_mb();
-        on_each_cpu(profile_nop, NULL, 1);
-        for_each_online_cpu(cpu) {
-                struct page *page;
-
-                if (per_cpu(cpu_profile_hits, cpu)[0]) {
-                        page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
-                        per_cpu(cpu_profile_hits, cpu)[0] = NULL;
-                        __free_page(page);
-                }
-                if (per_cpu(cpu_profile_hits, cpu)[1]) {
-                        page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
-                        per_cpu(cpu_profile_hits, cpu)[1] = NULL;
-                        __free_page(page);
-                }
-        }
-        return -1;
-}
-#else
-#define create_hash_tables()                    ({ 0; })
+        struct proc_dir_entry *entry;
+#ifdef CONFIG_SMP
+        enum cpuhp_state online_state;
 #endif
 
-int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */
-{
-        struct proc_dir_entry *entry;
         int err = 0;
 
         if (!prof_on)
                 return 0;
-
-        cpu_notifier_register_begin();
-
-        if (create_hash_tables()) {
-                err = -ENOMEM;
-                goto out;
-        }
-
+#ifdef CONFIG_SMP
+        err = cpuhp_setup_state(CPUHP_PROFILE_PREPARE, "PROFILE_PREPARE",
+                                profile_prepare_cpu, profile_dead_cpu);
+        if (err)
+                return err;
+
+        err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "AP_PROFILE_ONLINE",
+                                profile_online_cpu, NULL);
+        if (err < 0)
+                goto err_state_prep;
+        online_state = err;
+        err = 0;
+#endif
         entry = proc_create("profile", S_IWUSR | S_IRUGO,
                             NULL, &proc_profile_operations);
         if (!entry)
-                goto out;
+                goto err_state_onl;
         proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
-        __hotcpu_notifier(profile_cpu_callback, 0);
 
-out:
-        cpu_notifier_register_done();
+        return err;
+err_state_onl:
+#ifdef CONFIG_SMP
+        cpuhp_remove_state(online_state);
+err_state_prep:
+        cpuhp_remove_state(CPUHP_PROFILE_PREPARE);
+#endif
         return err;
 }
 subsys_initcall(create_proc_profile);